package com.sinsz.nacos;

import java.io.File;
import java.io.IOException;
import java.net.JarURLConnection;
import java.net.URL;
import java.net.URLDecoder;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;

/**
 * 类寻找工具
 *
 * @author chenjianbo
 */
public final class ClassUtils {

    private ClassUtils() {
    }

    /**
     * 通过包名获取包内所有类
     *
     * @param pkg
     * @return list
     */
    public synchronized static List<Class<?>> getAllClassByPackageName(Package pkg) {
        String packageName = pkg.getName();
        return getClasses(packageName);
    }

    /**
     * 通过接口名取得某个接口下所有实现这个接口的类
     *
     * @param c
     * @return list
     */
    public synchronized static List<Class<?>> getAllClassByInterface(Class<?> c) {
        List<Class<?>> returnClassList = null;
        if (c.isInterface()) {
            String packageName = c.getPackage().getName();
            List<Class<?>> allClass = getClasses(packageName);
            if (allClass != null) {
                returnClassList = new ArrayList<>();
                for (Class<?> cls : allClass) {
                    if (c.isAssignableFrom(cls)) {
                        if (!c.equals(cls)) {
                            returnClassList.add(cls);
                        }
                    }
                }
            }
        }
        return returnClassList;
    }

    /**
     * 从包package中获取所有的Class
     *
     * @param packageName
     * @return list
     */
    private synchronized static List<Class<?>> getClasses(String packageName) {
        List<Class<?>> classes = new ArrayList<Class<?>>();
        String packageDirName = packageName.replace('.', '/');
        Enumeration<URL> dirs;
        try {
            dirs = Thread.currentThread().getContextClassLoader().getResources(packageDirName);
            while (dirs.hasMoreElements()) {
                URL url = dirs.nextElement();
                String protocol = url.getProtocol();
                if ("file".equals(protocol)) {
                    String filePath = URLDecoder.decode(url.getFile(), "UTF-8");
                    findAndAddClassesInPackageByFile(packageName, filePath, true, classes);
                } else if ("jar".equals(protocol)) {
                    JarFile jar;
                    try {
                        jar = ((JarURLConnection) url.openConnection()).getJarFile();
                        Enumeration<JarEntry> entries = jar.entries();
                        while (entries.hasMoreElements()) {
                            JarEntry entry = entries.nextElement();
                            String name = entry.getName();
                            if (name.charAt(0) == '/') {
                                name = name.substring(1);
                            }
                            if (name.startsWith(packageDirName)) {
                                int idx = name.lastIndexOf('/');
                                if (idx != -1) {
                                    packageName = name.substring(0, idx).replace('/', '.');
                                }
                                if (name.endsWith(".class") && !entry.isDirectory()) {
                                    String className = name.substring(packageName.length() + 1, name.length() - 6);
                                    try {
                                        classes.add(Class.forName(packageName + '.' + className));
                                    } catch (ClassNotFoundException e) {
                                        e.printStackTrace();
                                    }
                                }
                            }
                        }
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return classes;
    }

    /**
     * 以文件的形式来获取包下的所有Class
     *
     * @param packageName
     * @param packagePath
     * @param recursive
     * @param classes
     */
    private static void findAndAddClassesInPackageByFile(
            String packageName,
            String packagePath,
            final boolean
                    recursive,
            List<Class<?>> classes) {
        File dir = new File(packagePath);
        if (!dir.exists() || !dir.isDirectory()) {
            return;
        }
        File[] dirfiles = dir.listFiles(file -> (recursive && file.isDirectory()) || (file.getName().endsWith("" +
                ".class")));
        assert dirfiles != null;
        for (File file : dirfiles) {
            if (file.isDirectory()) {
                findAndAddClassesInPackageByFile(packageName + "." + file.getName(), file.getAbsolutePath(),
                        recursive, classes);
            } else {
                String className = file.getName().substring(0, file.getName().length() - 6);
                try {
                    classes.add(Class.forName(packageName + '.' + className));
                } catch (ClassNotFoundException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}
